1. The Field of the Invention
The present invention relates to systems and methods for improving band offset in semiconductor light emitters. More particularly, the present invention relates to systems and methods for improving band offset in semiconductor light emitters for improved temperature performance.
2. Background and Relevant Art
Semiconductor light emitters can take a variety of different forms. Light emitting diodes (LEDs), vertical cavity surface emitting lasers (VCSELs), and edge emitting lasers are examples of semiconductor light emitters. Semiconductor light emitters can also emit light at various wavelengths. However, the ability to emit light at shorter wavelengths (in the visible spectrum, for example) faces several challenges, particularly in VCSELs.
One of the system materials currently used to produce VCSELs emitting a wavelength in the visible spectrum is AlInGaP (Aluminum Indium Gallium Phosphide). In fact, AlInGaP materials are often used in lasers that emit light at wavelengths in the red region of the visible spectrum. However, the wavelengths that can be emitted using an AlInGaP system material are typically limited.
Some of the factors that limit the range of wavelengths that can be emitted by an AlInGaP device include the inability to obtain sufficiently high p-type doping levels, low hole mobility, and a small conduction band offset. The small conduction band offset can result in poor carrier confinement, which impacts the quality of the device.
For example, AlInGaP VCSELs that are designed to be red light emitters (emitting a wavelength on the order of 690-630 nm) face challenges that are related to both temperature and conduction band offset. The thermal distribution of energy can excite carriers out of the quantum wells. If the carriers are not in the quantum wells, then the carriers cannot recombine to produce light. This problem is further complicated by the low conduction band offset. In other words, the quantum wells of AlInGaP devices have shallow wells. The shallowness of the wells combined with temperature leads to poor carrier confinement and carrier leakage.
In addition, AlInGaP devices often have a close indirect conduction band in addition to a low conduction band offset. The close indirect conduction band can also lead to carrier leakage from the quantum wells and further requires a phonon to conserve momentum of the photon. Thus, the low conduction band offset, the close indirect conduction band, and higher temperatures result in poor carrier confinement and degrade the high temperature performance of AlInGaP devices.